Brake or clutch units have one or more friction plates that preferably have an essentially annular shape. Multiple-plate clutches are based on two or more friction plates generally called discs. A first group of these discs, known as the outer discs, are joined in a rotationally fixed manner, for example by means of appropriate splining, to an outer disc carrier that is coupled to a first shaft, for example an input drive shaft, and a second group of these discs, known as the inner discs, are joined in a rotationally fixed manner to an inner disc carrier that is coupled to a second shaft, for example an output drive shaft. The discs of the two groups engage one another in alternation, forming a disc pack. In this context, the outer discs and inner discs are capable of limited motion toward one another in the axial direction, thereby frictionally engaging in pairs at their adjoining faces. A distinction is drawn between discs with and without friction lining.
Friction plates or discs with friction lining preferably have a metallic, annular core plate which carries, on one or both faces, a friction lining made, for example of a fibrous material produced from organic or inorganic substances. Friction plates without friction linings, known as steel discs, consist essentially of the core plate alone.
Friction linings of the aforementioned type were initially designed as a single piece. Since the fibrous material is generally present in the form of sheets from which the friction linings are cut or separated, considerable unusable cutting waste results.
In order to save on friction material, it has thus subsequently become common practice to cut or stamp sections of friction lining in the form of segments, especially segments of an annulus, from a thin (fibrous) material and to assemble them on the core plate into an, e.g., annular friction lining consisting of many segments arranged in the circumferential direction, or if desired the radial direction as well. A variety of methods with greater or lesser cutting waste are used in this context. Referenced here by way of example are the implementations in U.S. Pat. Nos. 4,260,047, 6,019,205, WO 99/64755 A1 and U.S. Pat. No. 6,409,006 B1.
Essentially the same need for economy of material and the associated cost reduction in manufacturing exists for the metallic core plates used. In similar fashion, U.S. Pat. No. 4,674,616 thus proposes also assembling from multiple annular segments the metallic core plate of a disc provided on both sides with a friction lining made of a fibrous material. In order to achieve adequate mechanical stability of such a disc with a core plate assembled from annular segments, the individual annular segments have projections and recesses with complementary shapes at their ends where they are assembled. Moreover, the segments of the likewise segmented, and preferably fibrous, friction lining can be arranged to be offset circumferentially relative to the core plate segments.
Even though this design of discs having a friction lining made of fibrous material has in essence proven its utility, its mechanical stability is not always adequate. In particular, discs with no friction lining or with a friction lining on only one side frequently cannot be manufactured with the requisite mechanical stability when the core plate is segmented.
Consequently, the object of the invention is to provide a segmented core plate for a disc, and also a disc with a segmented core plate, which have greater mechanical stability. An additional object is to specify a method for manufacturing the same.
This object is attained in accordance with the invention by a segmented core plate for a disc, a disc with segmented core plate, a method for manufacturing a segmented core plate, and a method for manufacturing a disc with segmented core plate.
It has become apparent that a disc produced according to the teaching of U.S. Pat. No. 4,674,616 frequently does not achieve the requisite mechanical stability because the complementarity of shapes of the connected core plate segments cannot be manufactured with sufficient precision. As a result, not only is movement between adjacent segments possible perpendicular to the friction surface, but tilting of adjacent segments may also occur. While the fibrous material of the friction lining and the segments themselves have adequate strength to prevent parallel displacement of adjacent core plate segments, the aforementioned tipping motions cannot be adequately absorbed by the friction lining and the segments themselves. This problem occurs to an even greater degree in segmented core plates without friction linings in which mechanical stability must be achieved solely through the fastening of adjacent segments.